jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/comp/Flow.java@12f99d1f23d9 (annotated)

src/share/classes/com/sun/tools/javac/comp/Flow.java@12f99d1f23d9 (annotated)

src/share/classes/com/sun/tools/javac/comp/Flow.java

Wed, 30 Apr 2014 23:29:43 +0100

author: pgovereau
date: Wed, 30 Apr 2014 23:29:43 +0100
changeset 2376: 12f99d1f23d9
parent 2370: acd64168cf8b
child 2408: 716f2466ddd0
permissions: -rw-r--r--

8039026: Definitely unassigned field can be accessed
Reviewed-by: vromero, jlahoda

 /*
  * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 //todo: one might eliminate uninits.andSets when monotonic
 package com.sun.tools.javac.comp;
 import java.util.HashMap;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.tree.*;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.tree.JCTree.*;
 import static com.sun.tools.javac.code.Flags.*;
 import static com.sun.tools.javac.code.Flags.BLOCK;
 import static com.sun.tools.javac.code.Kinds.*;
 import static com.sun.tools.javac.code.TypeTag.BOOLEAN;
 import static com.sun.tools.javac.code.TypeTag.VOID;
 import static com.sun.tools.javac.tree.JCTree.Tag.*;
 /** This pass implements dataflow analysis for Java programs though
  *  different AST visitor steps. Liveness analysis (see AliveAnalyzer) checks that
  *  every statement is reachable. Exception analysis (see FlowAnalyzer) ensures that
  *  every checked exception that is thrown is declared or caught.  Definite assignment analysis
  *  (see AssignAnalyzer) ensures that each variable is assigned when used.  Definite
  *  unassignment analysis (see AssignAnalyzer) in ensures that no final variable
  *  is assigned more than once. Finally, local variable capture analysis (see CaptureAnalyzer)
  *  determines that local variables accessed within the scope of an inner class/lambda
  *  are either final or effectively-final.
  *
  *  <p>The JLS has a number of problems in the
  *  specification of these flow analysis problems. This implementation
  *  attempts to address those issues.
  *
  *  <p>First, there is no accommodation for a finally clause that cannot
  *  complete normally. For liveness analysis, an intervening finally
  *  clause can cause a break, continue, or return not to reach its
  *  target.  For exception analysis, an intervening finally clause can
  *  cause any exception to be "caught".  For DA/DU analysis, the finally
  *  clause can prevent a transfer of control from propagating DA/DU
  *  state to the target.  In addition, code in the finally clause can
  *  affect the DA/DU status of variables.
  *
  *  <p>For try statements, we introduce the idea of a variable being
  *  definitely unassigned "everywhere" in a block.  A variable V is
  *  "unassigned everywhere" in a block iff it is unassigned at the
  *  beginning of the block and there is no reachable assignment to V
  *  in the block.  An assignment V=e is reachable iff V is not DA
  *  after e.  Then we can say that V is DU at the beginning of the
  *  catch block iff V is DU everywhere in the try block.  Similarly, V
  *  is DU at the beginning of the finally block iff V is DU everywhere
  *  in the try block and in every catch block.  Specifically, the
  *  following bullet is added to 16.2.2
  *  <pre>
  *      V is <em>unassigned everywhere</em> in a block if it is
  *      unassigned before the block and there is no reachable
  *      assignment to V within the block.
  *  </pre>
  *  <p>In 16.2.15, the third bullet (and all of its sub-bullets) for all
  *  try blocks is changed to
  *  <pre>
  *      V is definitely unassigned before a catch block iff V is
  *      definitely unassigned everywhere in the try block.
  *  </pre>
  *  <p>The last bullet (and all of its sub-bullets) for try blocks that
  *  have a finally block is changed to
  *  <pre>
  *      V is definitely unassigned before the finally block iff
  *      V is definitely unassigned everywhere in the try block
  *      and everywhere in each catch block of the try statement.
  *  </pre>
  *  <p>In addition,
  *  <pre>
  *      V is definitely assigned at the end of a constructor iff
  *      V is definitely assigned after the block that is the body
  *      of the constructor and V is definitely assigned at every
  *      return that can return from the constructor.
  *  </pre>
  *  <p>In addition, each continue statement with the loop as its target
  *  is treated as a jump to the end of the loop body, and "intervening"
  *  finally clauses are treated as follows: V is DA "due to the
  *  continue" iff V is DA before the continue statement or V is DA at
  *  the end of any intervening finally block.  V is DU "due to the
  *  continue" iff any intervening finally cannot complete normally or V
  *  is DU at the end of every intervening finally block.  This "due to
  *  the continue" concept is then used in the spec for the loops.
  *
  *  <p>Similarly, break statements must consider intervening finally
  *  blocks.  For liveness analysis, a break statement for which any
  *  intervening finally cannot complete normally is not considered to
  *  cause the target statement to be able to complete normally. Then
  *  we say V is DA "due to the break" iff V is DA before the break or
  *  V is DA at the end of any intervening finally block.  V is DU "due
  *  to the break" iff any intervening finally cannot complete normally
  *  or V is DU at the break and at the end of every intervening
  *  finally block.  (I suspect this latter condition can be
  *  simplified.)  This "due to the break" is then used in the spec for
  *  all statements that can be "broken".
  *
  *  <p>The return statement is treated similarly.  V is DA "due to a
  *  return statement" iff V is DA before the return statement or V is
  *  DA at the end of any intervening finally block.  Note that we
  *  don't have to worry about the return expression because this
  *  concept is only used for construcrors.
  *
  *  <p>There is no spec in the JLS for when a variable is definitely
  *  assigned at the end of a constructor, which is needed for final
  *  fields (8.3.1.2).  We implement the rule that V is DA at the end
  *  of the constructor iff it is DA and the end of the body of the
  *  constructor and V is DA "due to" every return of the constructor.
  *
  *  <p>Intervening finally blocks similarly affect exception analysis.  An
  *  intervening finally that cannot complete normally allows us to ignore
  *  an otherwise uncaught exception.
  *
  *  <p>To implement the semantics of intervening finally clauses, all
  *  nonlocal transfers (break, continue, return, throw, method call that
  *  can throw a checked exception, and a constructor invocation that can
  *  thrown a checked exception) are recorded in a queue, and removed
  *  from the queue when we complete processing the target of the
  *  nonlocal transfer.  This allows us to modify the queue in accordance
  *  with the above rules when we encounter a finally clause.  The only
  *  exception to this [no pun intended] is that checked exceptions that
  *  are known to be caught or declared to be caught in the enclosing
  *  method are not recorded in the queue, but instead are recorded in a
  *  global variable "{@code Set<Type> thrown}" that records the type of all
  *  exceptions that can be thrown.
  *
  *  <p>Other minor issues the treatment of members of other classes
  *  (always considered DA except that within an anonymous class
  *  constructor, where DA status from the enclosing scope is
  *  preserved), treatment of the case expression (V is DA before the
  *  case expression iff V is DA after the switch expression),
  *  treatment of variables declared in a switch block (the implied
  *  DA/DU status after the switch expression is DU and not DA for
  *  variables defined in a switch block), the treatment of boolean ?:
  *  expressions (The JLS rules only handle b and c non-boolean; the
  *  new rule is that if b and c are boolean valued, then V is
  *  (un)assigned after a?b:c when true/false iff V is (un)assigned
  *  after b when true/false and V is (un)assigned after c when
  *  true/false).
  *
  *  <p>There is the remaining question of what syntactic forms constitute a
  *  reference to a variable.  It is conventional to allow this.x on the
  *  left-hand-side to initialize a final instance field named x, yet
  *  this.x isn't considered a "use" when appearing on a right-hand-side
  *  in most implementations.  Should parentheses affect what is
  *  considered a variable reference?  The simplest rule would be to
  *  allow unqualified forms only, parentheses optional, and phase out
  *  support for assigning to a final field via this.x.
  *
  *  <p><b>This is NOT part of any supported API.
  *  If you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public class Flow {
     protected static final Context.Key<Flow> flowKey =
         new Context.Key<Flow>();
     private final Names names;
     private final Log log;
     private final Symtab syms;
     private final Types types;
     private final Check chk;
     private       TreeMaker make;
     private final Resolve rs;
     private final JCDiagnostic.Factory diags;
     private Env<AttrContext> attrEnv;
     private       Lint lint;
     private final boolean allowImprovedRethrowAnalysis;
     private final boolean allowImprovedCatchAnalysis;
     private final boolean allowEffectivelyFinalInInnerClasses;
     private final boolean enforceThisDotInit;
     public static Flow instance(Context context) {
         Flow instance = context.get(flowKey);
         if (instance == null)
             instance = new Flow(context);
         return instance;
     }
     public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
         new AliveAnalyzer().analyzeTree(env, make);
         new AssignAnalyzer(log, syms, lint, names, enforceThisDotInit).analyzeTree(env);
         new FlowAnalyzer().analyzeTree(env, make);
         new CaptureAnalyzer().analyzeTree(env, make);
     }
     public void analyzeLambda(Env<AttrContext> env, JCLambda that, TreeMaker make, boolean speculative) {
         Log.DiagnosticHandler diagHandler = null;
         //we need to disable diagnostics temporarily; the problem is that if
         //a lambda expression contains e.g. an unreachable statement, an error
         //message will be reported and will cause compilation to skip the flow analyis
         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
         //related errors, which will allow for more errors to be detected
         if (!speculative) {
             diagHandler = new Log.DiscardDiagnosticHandler(log);
         }
         try {
             new AliveAnalyzer().analyzeTree(env, that, make);
         } finally {
             if (!speculative) {
                 log.popDiagnosticHandler(diagHandler);
             }
         }
     }
     public List<Type> analyzeLambdaThrownTypes(Env<AttrContext> env, JCLambda that, TreeMaker make) {
         //we need to disable diagnostics temporarily; the problem is that if
         //a lambda expression contains e.g. an unreachable statement, an error
         //message will be reported and will cause compilation to skip the flow analyis
         //step - if we suppress diagnostics, we won't stop at Attr for flow-analysis
         //related errors, which will allow for more errors to be detected
         Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
         try {
             new AssignAnalyzer(log, syms, lint, names, enforceThisDotInit).analyzeTree(env);
             LambdaFlowAnalyzer flowAnalyzer = new LambdaFlowAnalyzer();
             flowAnalyzer.analyzeTree(env, that, make);
             return flowAnalyzer.inferredThrownTypes;
         } finally {
             log.popDiagnosticHandler(diagHandler);
         }
     }
     /**
      * Definite assignment scan mode
      */
     enum FlowKind {
         /**
          * This is the normal DA/DU analysis mode
          */
         NORMAL("var.might.already.be.assigned", false),
         /**
          * This is the speculative DA/DU analysis mode used to speculatively
          * derive assertions within loop bodies
          */
         SPECULATIVE_LOOP("var.might.be.assigned.in.loop", true);
         final String errKey;
         final boolean isFinal;
         FlowKind(String errKey, boolean isFinal) {
             this.errKey = errKey;
             this.isFinal = isFinal;
         }
         boolean isFinal() {
             return isFinal;
         }
     }
     protected Flow(Context context) {
         context.put(flowKey, this);
         names = Names.instance(context);
         log = Log.instance(context);
         syms = Symtab.instance(context);
         types = Types.instance(context);
         chk = Check.instance(context);
         lint = Lint.instance(context);
         rs = Resolve.instance(context);
         diags = JCDiagnostic.Factory.instance(context);
         Source source = Source.instance(context);
         allowImprovedRethrowAnalysis = source.allowImprovedRethrowAnalysis();
         allowImprovedCatchAnalysis = source.allowImprovedCatchAnalysis();
         allowEffectivelyFinalInInnerClasses = source.allowEffectivelyFinalInInnerClasses();
         enforceThisDotInit = source.enforceThisDotInit();
     }
     /**
      * Base visitor class for all visitors implementing dataflow analysis logic.
      * This class define the shared logic for handling jumps (break/continue statements).
      */
     static abstract class BaseAnalyzer<P extends BaseAnalyzer.PendingExit> extends TreeScanner {
         enum JumpKind {
             BREAK(JCTree.Tag.BREAK) {
                 @Override
                 JCTree getTarget(JCTree tree) {
                     return ((JCBreak)tree).target;
                 }
             },
             CONTINUE(JCTree.Tag.CONTINUE) {
                 @Override
                 JCTree getTarget(JCTree tree) {
                     return ((JCContinue)tree).target;
                 }
             };
             final JCTree.Tag treeTag;
             private JumpKind(Tag treeTag) {
                 this.treeTag = treeTag;
             }
             abstract JCTree getTarget(JCTree tree);
         }
         /** The currently pending exits that go from current inner blocks
          *  to an enclosing block, in source order.
          */
         ListBuffer<P> pendingExits;
         /** A pending exit.  These are the statements return, break, and
          *  continue.  In addition, exception-throwing expressions or
          *  statements are put here when not known to be caught.  This
          *  will typically result in an error unless it is within a
          *  try-finally whose finally block cannot complete normally.
          */
         static class PendingExit {
             JCTree tree;
             PendingExit(JCTree tree) {
                 this.tree = tree;
             }
             void resolveJump(JCTree tree) {
                 //do nothing
             }
         }
         abstract void markDead(JCTree tree);
         /** Record an outward transfer of control. */
         void recordExit(JCTree tree, P pe) {
             pendingExits.append(pe);
             markDead(tree);
         }
         /** Resolve all jumps of this statement. */
         private boolean resolveJump(JCTree tree,
                         ListBuffer<P> oldPendingExits,
                         JumpKind jk) {
             boolean resolved = false;
             List<P> exits = pendingExits.toList();
             pendingExits = oldPendingExits;
             for (; exits.nonEmpty(); exits = exits.tail) {
                 P exit = exits.head;
                 if (exit.tree.hasTag(jk.treeTag) &&
                         jk.getTarget(exit.tree) == tree) {
                     exit.resolveJump(tree);
                     resolved = true;
                 } else {
                     pendingExits.append(exit);
                 }
             }
             return resolved;
         }
         /** Resolve all continues of this statement. */
         boolean resolveContinues(JCTree tree) {
             return resolveJump(tree, new ListBuffer<P>(), JumpKind.CONTINUE);
         }
         /** Resolve all breaks of this statement. */
         boolean resolveBreaks(JCTree tree, ListBuffer<P> oldPendingExits) {
             return resolveJump(tree, oldPendingExits, JumpKind.BREAK);
         }
         @Override
         public void scan(JCTree tree) {
             if (tree != null && (
                     tree.type == null ||
                     tree.type != Type.stuckType)) {
                 super.scan(tree);
             }
         }
     }
     /**
      * This pass implements the first step of the dataflow analysis, namely
      * the liveness analysis check. This checks that every statement is reachable.
      * The output of this analysis pass are used by other analyzers. This analyzer
      * sets the 'finallyCanCompleteNormally' field in the JCTry class.
      */
     class AliveAnalyzer extends BaseAnalyzer<BaseAnalyzer.PendingExit> {
         /** A flag that indicates whether the last statement could
          *  complete normally.
          */
         private boolean alive;
         @Override
         void markDead(JCTree tree) {
             alive = false;
         }
     /*************************************************************************
      * Visitor methods for statements and definitions
      *************************************************************************/
         /** Analyze a definition.
          */
         void scanDef(JCTree tree) {
             scanStat(tree);
             if (tree != null && tree.hasTag(JCTree.Tag.BLOCK) && !alive) {
                 log.error(tree.pos(),
                           "initializer.must.be.able.to.complete.normally");
             }
         }
         /** Analyze a statement. Check that statement is reachable.
          */
         void scanStat(JCTree tree) {
             if (!alive && tree != null) {
                 log.error(tree.pos(), "unreachable.stmt");
                 if (!tree.hasTag(SKIP)) alive = true;
             }
             scan(tree);
         }
         /** Analyze list of statements.
          */
         void scanStats(List<? extends JCStatement> trees) {
             if (trees != null)
                 for (List<? extends JCStatement> l = trees; l.nonEmpty(); l = l.tail)
                     scanStat(l.head);
         }
         /* ------------ Visitor methods for various sorts of trees -------------*/
         public void visitClassDef(JCClassDecl tree) {
             if (tree.sym == null) return;
             boolean alivePrev = alive;
             ListBuffer<PendingExit> pendingExitsPrev = pendingExits;
             Lint lintPrev = lint;
             pendingExits = new ListBuffer<PendingExit>();
             lint = lint.augment(tree.sym);
             try {
                 // process all the static initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) != 0) {
                         scanDef(l.head);
                     }
                 }
                 // process all the instance initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) == 0) {
                         scanDef(l.head);
                     }
                 }
                 // process all the methods
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(METHODDEF)) {
                         scan(l.head);
                     }
                 }
             } finally {
                 pendingExits = pendingExitsPrev;
                 alive = alivePrev;
                 lint = lintPrev;
             }
         }
         public void visitMethodDef(JCMethodDecl tree) {
             if (tree.body == null) return;
             Lint lintPrev = lint;
             lint = lint.augment(tree.sym);
             Assert.check(pendingExits.isEmpty());
             try {
                 alive = true;
                 scanStat(tree.body);
                 if (alive && !tree.sym.type.getReturnType().hasTag(VOID))
                     log.error(TreeInfo.diagEndPos(tree.body), "missing.ret.stmt");
                 List<PendingExit> exits = pendingExits.toList();
                 pendingExits = new ListBuffer<PendingExit>();
                 while (exits.nonEmpty()) {
                     PendingExit exit = exits.head;
                     exits = exits.tail;
                     Assert.check(exit.tree.hasTag(RETURN));
                 }
             } finally {
                 lint = lintPrev;
             }
         }
         public void visitVarDef(JCVariableDecl tree) {
             if (tree.init != null) {
                 Lint lintPrev = lint;
                 lint = lint.augment(tree.sym);
                 try{
                     scan(tree.init);
                 } finally {
                     lint = lintPrev;
                 }
             }
         }
         public void visitBlock(JCBlock tree) {
             scanStats(tree.stats);
         }
         public void visitDoLoop(JCDoWhileLoop tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<PendingExit>();
             scanStat(tree.body);
             alive |= resolveContinues(tree);
             scan(tree.cond);
             alive = alive && !tree.cond.type.isTrue();
             alive |= resolveBreaks(tree, prevPendingExits);
         }
         public void visitWhileLoop(JCWhileLoop tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<PendingExit>();
             scan(tree.cond);
             alive = !tree.cond.type.isFalse();
             scanStat(tree.body);
             alive |= resolveContinues(tree);
             alive = resolveBreaks(tree, prevPendingExits) ||
                 !tree.cond.type.isTrue();
         }
         public void visitForLoop(JCForLoop tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             scanStats(tree.init);
             pendingExits = new ListBuffer<PendingExit>();
             if (tree.cond != null) {
                 scan(tree.cond);
                 alive = !tree.cond.type.isFalse();
             } else {
                 alive = true;
             }
             scanStat(tree.body);
             alive |= resolveContinues(tree);
             scan(tree.step);
             alive = resolveBreaks(tree, prevPendingExits) ||
                 tree.cond != null && !tree.cond.type.isTrue();
         }
         public void visitForeachLoop(JCEnhancedForLoop tree) {
             visitVarDef(tree.var);
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             scan(tree.expr);
             pendingExits = new ListBuffer<PendingExit>();
             scanStat(tree.body);
             alive |= resolveContinues(tree);
             resolveBreaks(tree, prevPendingExits);
             alive = true;
         }
         public void visitLabelled(JCLabeledStatement tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<PendingExit>();
             scanStat(tree.body);
             alive |= resolveBreaks(tree, prevPendingExits);
         }
         public void visitSwitch(JCSwitch tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<PendingExit>();
             scan(tree.selector);
             boolean hasDefault = false;
             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
                 alive = true;
                 JCCase c = l.head;
                 if (c.pat == null)
                     hasDefault = true;
                 else
                     scan(c.pat);
                 scanStats(c.stats);
                 // Warn about fall-through if lint switch fallthrough enabled.
                 if (alive &&
                     lint.isEnabled(Lint.LintCategory.FALLTHROUGH) &&
                     c.stats.nonEmpty() && l.tail.nonEmpty())
                     log.warning(Lint.LintCategory.FALLTHROUGH,
                                 l.tail.head.pos(),
                                 "possible.fall-through.into.case");
             }
             if (!hasDefault) {
                 alive = true;
             }
             alive |= resolveBreaks(tree, prevPendingExits);
         }
         public void visitTry(JCTry tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<PendingExit>();
             for (JCTree resource : tree.resources) {
                 if (resource instanceof JCVariableDecl) {
                     JCVariableDecl vdecl = (JCVariableDecl) resource;
                     visitVarDef(vdecl);
                 } else if (resource instanceof JCExpression) {
                     scan((JCExpression) resource);
                 } else {
                     throw new AssertionError(tree);  // parser error
                 }
             }
             scanStat(tree.body);
             boolean aliveEnd = alive;
             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
                 alive = true;
                 JCVariableDecl param = l.head.param;
                 scan(param);
                 scanStat(l.head.body);
                 aliveEnd |= alive;
             }
             if (tree.finalizer != null) {
                 ListBuffer<PendingExit> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 alive = true;
                 scanStat(tree.finalizer);
                 tree.finallyCanCompleteNormally = alive;
                 if (!alive) {
                     if (lint.isEnabled(Lint.LintCategory.FINALLY)) {
                         log.warning(Lint.LintCategory.FINALLY,
                                 TreeInfo.diagEndPos(tree.finalizer),
                                 "finally.cannot.complete");
                     }
                 } else {
                     while (exits.nonEmpty()) {
                         pendingExits.append(exits.next());
                     }
                     alive = aliveEnd;
                 }
             } else {
                 alive = aliveEnd;
                 ListBuffer<PendingExit> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 while (exits.nonEmpty()) pendingExits.append(exits.next());
             }
         }
         @Override
         public void visitIf(JCIf tree) {
             scan(tree.cond);
             scanStat(tree.thenpart);
             if (tree.elsepart != null) {
                 boolean aliveAfterThen = alive;
                 alive = true;
                 scanStat(tree.elsepart);
                 alive = alive | aliveAfterThen;
             } else {
                 alive = true;
             }
         }
         public void visitBreak(JCBreak tree) {
             recordExit(tree, new PendingExit(tree));
         }
         public void visitContinue(JCContinue tree) {
             recordExit(tree, new PendingExit(tree));
         }
         public void visitReturn(JCReturn tree) {
             scan(tree.expr);
             recordExit(tree, new PendingExit(tree));
         }
         public void visitThrow(JCThrow tree) {
             scan(tree.expr);
             markDead(tree);
         }
         public void visitApply(JCMethodInvocation tree) {
             scan(tree.meth);
             scan(tree.args);
         }
         public void visitNewClass(JCNewClass tree) {
             scan(tree.encl);
             scan(tree.args);
             if (tree.def != null) {
                 scan(tree.def);
             }
         }
         @Override
         public void visitLambda(JCLambda tree) {
             if (tree.type != null &&
                     tree.type.isErroneous()) {
                 return;
             }
             ListBuffer<PendingExit> prevPending = pendingExits;
             boolean prevAlive = alive;
             try {
                 pendingExits = new ListBuffer<>();
                 alive = true;
                 scanStat(tree.body);
                 tree.canCompleteNormally = alive;
             }
             finally {
                 pendingExits = prevPending;
                 alive = prevAlive;
             }
         }
         public void visitTopLevel(JCCompilationUnit tree) {
             // Do nothing for TopLevel since each class is visited individually
         }
     /**************************************************************************
      * main method
      *************************************************************************/
         /** Perform definite assignment/unassignment analysis on a tree.
          */
         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
             analyzeTree(env, env.tree, make);
         }
         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
             try {
                 attrEnv = env;
                 Flow.this.make = make;
                 pendingExits = new ListBuffer<PendingExit>();
                 alive = true;
                 scan(tree);
             } finally {
                 pendingExits = null;
                 Flow.this.make = null;
             }
         }
     }
     /**
      * This pass implements the second step of the dataflow analysis, namely
      * the exception analysis. This is to ensure that every checked exception that is
      * thrown is declared or caught. The analyzer uses some info that has been set by
      * the liveliness analyzer.
      */
     class FlowAnalyzer extends BaseAnalyzer<FlowAnalyzer.FlowPendingExit> {
         /** A flag that indicates whether the last statement could
          *  complete normally.
          */
         HashMap<Symbol, List<Type>> preciseRethrowTypes;
         /** The current class being defined.
          */
         JCClassDecl classDef;
         /** The list of possibly thrown declarable exceptions.
          */
         List<Type> thrown;
         /** The list of exceptions that are either caught or declared to be
          *  thrown.
          */
         List<Type> caught;
         class FlowPendingExit extends BaseAnalyzer.PendingExit {
             Type thrown;
             FlowPendingExit(JCTree tree, Type thrown) {
                 super(tree);
                 this.thrown = thrown;
             }
         }
         @Override
         void markDead(JCTree tree) {
             //do nothing
         }
         /*-------------------- Exceptions ----------------------*/
         /** Complain that pending exceptions are not caught.
          */
         void errorUncaught() {
             for (FlowPendingExit exit = pendingExits.next();
                  exit != null;
                  exit = pendingExits.next()) {
                 if (classDef != null &&
                     classDef.pos == exit.tree.pos) {
                     log.error(exit.tree.pos(),
                             "unreported.exception.default.constructor",
                             exit.thrown);
                 } else if (exit.tree.hasTag(VARDEF) &&
                         ((JCVariableDecl)exit.tree).sym.isResourceVariable()) {
                     log.error(exit.tree.pos(),
                             "unreported.exception.implicit.close",
                             exit.thrown,
                             ((JCVariableDecl)exit.tree).sym.name);
                 } else {
                     log.error(exit.tree.pos(),
                             "unreported.exception.need.to.catch.or.throw",
                             exit.thrown);
                 }
             }
         }
         /** Record that exception is potentially thrown and check that it
          *  is caught.
          */
         void markThrown(JCTree tree, Type exc) {
             if (!chk.isUnchecked(tree.pos(), exc)) {
                 if (!chk.isHandled(exc, caught)) {
                     pendingExits.append(new FlowPendingExit(tree, exc));
                 }
                 thrown = chk.incl(exc, thrown);
             }
         }
     /*************************************************************************
      * Visitor methods for statements and definitions
      *************************************************************************/
         /* ------------ Visitor methods for various sorts of trees -------------*/
         public void visitClassDef(JCClassDecl tree) {
             if (tree.sym == null) return;
             JCClassDecl classDefPrev = classDef;
             List<Type> thrownPrev = thrown;
             List<Type> caughtPrev = caught;
             ListBuffer<FlowPendingExit> pendingExitsPrev = pendingExits;
             Lint lintPrev = lint;
             pendingExits = new ListBuffer<FlowPendingExit>();
             if (tree.name != names.empty) {
                 caught = List.nil();
             }
             classDef = tree;
             thrown = List.nil();
             lint = lint.augment(tree.sym);
             try {
                 // process all the static initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) != 0) {
                         scan(l.head);
                         errorUncaught();
                     }
                 }
                 // add intersection of all thrown clauses of initial constructors
                 // to set of caught exceptions, unless class is anonymous.
                 if (tree.name != names.empty) {
                     boolean firstConstructor = true;
                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                         if (TreeInfo.isInitialConstructor(l.head)) {
                             List<Type> mthrown =
                                 ((JCMethodDecl) l.head).sym.type.getThrownTypes();
                             if (firstConstructor) {
                                 caught = mthrown;
                                 firstConstructor = false;
                             } else {
                                 caught = chk.intersect(mthrown, caught);
                             }
                         }
                     }
                 }
                 // process all the instance initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) == 0) {
                         scan(l.head);
                         errorUncaught();
                     }
                 }
                 // in an anonymous class, add the set of thrown exceptions to
                 // the throws clause of the synthetic constructor and propagate
                 // outwards.
                 // Changing the throws clause on the fly is okay here because
                 // the anonymous constructor can't be invoked anywhere else,
                 // and its type hasn't been cached.
                 if (tree.name == names.empty) {
                     for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                         if (TreeInfo.isInitialConstructor(l.head)) {
                             JCMethodDecl mdef = (JCMethodDecl)l.head;
                             mdef.thrown = make.Types(thrown);
                             mdef.sym.type = types.createMethodTypeWithThrown(mdef.sym.type, thrown);
                         }
                     }
                     thrownPrev = chk.union(thrown, thrownPrev);
                 }
                 // process all the methods
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(METHODDEF)) {
                         scan(l.head);
                         errorUncaught();
                     }
                 }
                 thrown = thrownPrev;
             } finally {
                 pendingExits = pendingExitsPrev;
                 caught = caughtPrev;
                 classDef = classDefPrev;
                 lint = lintPrev;
             }
         }
         public void visitMethodDef(JCMethodDecl tree) {
             if (tree.body == null) return;
             List<Type> caughtPrev = caught;
             List<Type> mthrown = tree.sym.type.getThrownTypes();
             Lint lintPrev = lint;
             lint = lint.augment(tree.sym);
             Assert.check(pendingExits.isEmpty());
             try {
                 for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
                     JCVariableDecl def = l.head;
                     scan(def);
                 }
                 if (TreeInfo.isInitialConstructor(tree))
                     caught = chk.union(caught, mthrown);
                 else if ((tree.sym.flags() & (BLOCK | STATIC)) != BLOCK)
                     caught = mthrown;
                 // else we are in an instance initializer block;
                 // leave caught unchanged.
                 scan(tree.body);
                 List<FlowPendingExit> exits = pendingExits.toList();
                 pendingExits = new ListBuffer<FlowPendingExit>();
                 while (exits.nonEmpty()) {
                     FlowPendingExit exit = exits.head;
                     exits = exits.tail;
                     if (exit.thrown == null) {
                         Assert.check(exit.tree.hasTag(RETURN));
                     } else {
                         // uncaught throws will be reported later
                         pendingExits.append(exit);
                     }
                 }
             } finally {
                 caught = caughtPrev;
                 lint = lintPrev;
             }
         }
         public void visitVarDef(JCVariableDecl tree) {
             if (tree.init != null) {
                 Lint lintPrev = lint;
                 lint = lint.augment(tree.sym);
                 try{
                     scan(tree.init);
                 } finally {
                     lint = lintPrev;
                 }
             }
         }
         public void visitBlock(JCBlock tree) {
             scan(tree.stats);
         }
         public void visitDoLoop(JCDoWhileLoop tree) {
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<FlowPendingExit>();
             scan(tree.body);
             resolveContinues(tree);
             scan(tree.cond);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitWhileLoop(JCWhileLoop tree) {
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<FlowPendingExit>();
             scan(tree.cond);
             scan(tree.body);
             resolveContinues(tree);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitForLoop(JCForLoop tree) {
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             scan(tree.init);
             pendingExits = new ListBuffer<FlowPendingExit>();
             if (tree.cond != null) {
                 scan(tree.cond);
             }
             scan(tree.body);
             resolveContinues(tree);
             scan(tree.step);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitForeachLoop(JCEnhancedForLoop tree) {
             visitVarDef(tree.var);
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             scan(tree.expr);
             pendingExits = new ListBuffer<FlowPendingExit>();
             scan(tree.body);
             resolveContinues(tree);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitLabelled(JCLabeledStatement tree) {
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<FlowPendingExit>();
             scan(tree.body);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitSwitch(JCSwitch tree) {
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<FlowPendingExit>();
             scan(tree.selector);
             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
                 JCCase c = l.head;
                 if (c.pat != null) {
                     scan(c.pat);
                 }
                 scan(c.stats);
             }
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitTry(JCTry tree) {
             List<Type> caughtPrev = caught;
             List<Type> thrownPrev = thrown;
             thrown = List.nil();
             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
                 List<JCExpression> subClauses = TreeInfo.isMultiCatch(l.head) ?
                         ((JCTypeUnion)l.head.param.vartype).alternatives :
                         List.of(l.head.param.vartype);
                 for (JCExpression ct : subClauses) {
                     caught = chk.incl(ct.type, caught);
                 }
             }
             ListBuffer<FlowPendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<FlowPendingExit>();
             for (JCTree resource : tree.resources) {
                 if (resource instanceof JCVariableDecl) {
                     JCVariableDecl vdecl = (JCVariableDecl) resource;
                     visitVarDef(vdecl);
                 } else if (resource instanceof JCExpression) {
                     scan((JCExpression) resource);
                 } else {
                     throw new AssertionError(tree);  // parser error
                 }
             }
             for (JCTree resource : tree.resources) {
                 List<Type> closeableSupertypes = resource.type.isCompound() ?
                     types.interfaces(resource.type).prepend(types.supertype(resource.type)) :
                     List.of(resource.type);
                 for (Type sup : closeableSupertypes) {
                     if (types.asSuper(sup, syms.autoCloseableType.tsym) != null) {
                         Symbol closeMethod = rs.resolveQualifiedMethod(tree,
                                 attrEnv,
                                 sup,
                                 names.close,
                                 List.<Type>nil(),
                                 List.<Type>nil());
                         Type mt = types.memberType(resource.type, closeMethod);
                         if (closeMethod.kind == MTH) {
                             for (Type t : mt.getThrownTypes()) {
                                 markThrown(resource, t);
                             }
                         }
                     }
                 }
             }
             scan(tree.body);
             List<Type> thrownInTry = allowImprovedCatchAnalysis ?
                 chk.union(thrown, List.of(syms.runtimeExceptionType, syms.errorType)) :
                 thrown;
             thrown = thrownPrev;
             caught = caughtPrev;
             List<Type> caughtInTry = List.nil();
             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
                 JCVariableDecl param = l.head.param;
                 List<JCExpression> subClauses = TreeInfo.isMultiCatch(l.head) ?
                         ((JCTypeUnion)l.head.param.vartype).alternatives :
                         List.of(l.head.param.vartype);
                 List<Type> ctypes = List.nil();
                 List<Type> rethrownTypes = chk.diff(thrownInTry, caughtInTry);
                 for (JCExpression ct : subClauses) {
                     Type exc = ct.type;
                     if (exc != syms.unknownType) {
                         ctypes = ctypes.append(exc);
                         if (types.isSameType(exc, syms.objectType))
                             continue;
                         checkCaughtType(l.head.pos(), exc, thrownInTry, caughtInTry);
                         caughtInTry = chk.incl(exc, caughtInTry);
                     }
                 }
                 scan(param);
                 preciseRethrowTypes.put(param.sym, chk.intersect(ctypes, rethrownTypes));
                 scan(l.head.body);
                 preciseRethrowTypes.remove(param.sym);
             }
             if (tree.finalizer != null) {
                 List<Type> savedThrown = thrown;
                 thrown = List.nil();
                 ListBuffer<FlowPendingExit> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 scan(tree.finalizer);
                 if (!tree.finallyCanCompleteNormally) {
                     // discard exits and exceptions from try and finally
                     thrown = chk.union(thrown, thrownPrev);
                 } else {
                     thrown = chk.union(thrown, chk.diff(thrownInTry, caughtInTry));
                     thrown = chk.union(thrown, savedThrown);
                     // FIX: this doesn't preserve source order of exits in catch
                     // versus finally!
                     while (exits.nonEmpty()) {
                         pendingExits.append(exits.next());
                     }
                 }
             } else {
                 thrown = chk.union(thrown, chk.diff(thrownInTry, caughtInTry));
                 ListBuffer<FlowPendingExit> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 while (exits.nonEmpty()) pendingExits.append(exits.next());
             }
         }
         @Override
         public void visitIf(JCIf tree) {
             scan(tree.cond);
             scan(tree.thenpart);
             if (tree.elsepart != null) {
                 scan(tree.elsepart);
             }
         }
         void checkCaughtType(DiagnosticPosition pos, Type exc, List<Type> thrownInTry, List<Type> caughtInTry) {
             if (chk.subset(exc, caughtInTry)) {
                 log.error(pos, "except.already.caught", exc);
             } else if (!chk.isUnchecked(pos, exc) &&
                     !isExceptionOrThrowable(exc) &&
                     !chk.intersects(exc, thrownInTry)) {
                 log.error(pos, "except.never.thrown.in.try", exc);
             } else if (allowImprovedCatchAnalysis) {
                 List<Type> catchableThrownTypes = chk.intersect(List.of(exc), thrownInTry);
                 // 'catchableThrownTypes' cannnot possibly be empty - if 'exc' was an
                 // unchecked exception, the result list would not be empty, as the augmented
                 // thrown set includes { RuntimeException, Error }; if 'exc' was a checked
                 // exception, that would have been covered in the branch above
                 if (chk.diff(catchableThrownTypes, caughtInTry).isEmpty() &&
                         !isExceptionOrThrowable(exc)) {
                     String key = catchableThrownTypes.length() == 1 ?
                             "unreachable.catch" :
                             "unreachable.catch.1";
                     log.warning(pos, key, catchableThrownTypes);
                 }
             }
         }
         //where
             private boolean isExceptionOrThrowable(Type exc) {
                 return exc.tsym == syms.throwableType.tsym ||
                     exc.tsym == syms.exceptionType.tsym;
             }
         public void visitBreak(JCBreak tree) {
             recordExit(tree, new FlowPendingExit(tree, null));
         }
         public void visitContinue(JCContinue tree) {
             recordExit(tree, new FlowPendingExit(tree, null));
         }
         public void visitReturn(JCReturn tree) {
             scan(tree.expr);
             recordExit(tree, new FlowPendingExit(tree, null));
         }
         public void visitThrow(JCThrow tree) {
             scan(tree.expr);
             Symbol sym = TreeInfo.symbol(tree.expr);
             if (sym != null &&
                 sym.kind == VAR &&
                 (sym.flags() & (FINAL | EFFECTIVELY_FINAL)) != 0 &&
                 preciseRethrowTypes.get(sym) != null &&
                 allowImprovedRethrowAnalysis) {
                 for (Type t : preciseRethrowTypes.get(sym)) {
                     markThrown(tree, t);
                 }
             }
             else {
                 markThrown(tree, tree.expr.type);
             }
             markDead(tree);
         }
         public void visitApply(JCMethodInvocation tree) {
             scan(tree.meth);
             scan(tree.args);
             for (List<Type> l = tree.meth.type.getThrownTypes(); l.nonEmpty(); l = l.tail)
                 markThrown(tree, l.head);
         }
         public void visitNewClass(JCNewClass tree) {
             scan(tree.encl);
             scan(tree.args);
            // scan(tree.def);
             for (List<Type> l = tree.constructorType.getThrownTypes();
                  l.nonEmpty();
                  l = l.tail) {
                 markThrown(tree, l.head);
             }
             List<Type> caughtPrev = caught;
             try {
                 // If the new class expression defines an anonymous class,
                 // analysis of the anonymous constructor may encounter thrown
                 // types which are unsubstituted type variables.
                 // However, since the constructor's actual thrown types have
                 // already been marked as thrown, it is safe to simply include
                 // each of the constructor's formal thrown types in the set of
                 // 'caught/declared to be thrown' types, for the duration of
                 // the class def analysis.
                 if (tree.def != null)
                     for (List<Type> l = tree.constructor.type.getThrownTypes();
                          l.nonEmpty();
                          l = l.tail) {
                         caught = chk.incl(l.head, caught);
                     }
                 scan(tree.def);
             }
             finally {
                 caught = caughtPrev;
             }
         }
         @Override
         public void visitLambda(JCLambda tree) {
             if (tree.type != null &&
                     tree.type.isErroneous()) {
                 return;
             }
             List<Type> prevCaught = caught;
             List<Type> prevThrown = thrown;
             ListBuffer<FlowPendingExit> prevPending = pendingExits;
             try {
                 pendingExits = new ListBuffer<>();
                 caught = tree.getDescriptorType(types).getThrownTypes();
                 thrown = List.nil();
                 scan(tree.body);
                 List<FlowPendingExit> exits = pendingExits.toList();
                 pendingExits = new ListBuffer<FlowPendingExit>();
                 while (exits.nonEmpty()) {
                     FlowPendingExit exit = exits.head;
                     exits = exits.tail;
                     if (exit.thrown == null) {
                         Assert.check(exit.tree.hasTag(RETURN));
                     } else {
                         // uncaught throws will be reported later
                         pendingExits.append(exit);
                     }
                 }
                 errorUncaught();
             } finally {
                 pendingExits = prevPending;
                 caught = prevCaught;
                 thrown = prevThrown;
             }
         }
         public void visitTopLevel(JCCompilationUnit tree) {
             // Do nothing for TopLevel since each class is visited individually
         }
     /**************************************************************************
      * main method
      *************************************************************************/
         /** Perform definite assignment/unassignment analysis on a tree.
          */
         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
             analyzeTree(env, env.tree, make);
         }
         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
             try {
                 attrEnv = env;
                 Flow.this.make = make;
                 pendingExits = new ListBuffer<FlowPendingExit>();
                 preciseRethrowTypes = new HashMap<Symbol, List<Type>>();
                 this.thrown = this.caught = null;
                 this.classDef = null;
                 scan(tree);
             } finally {
                 pendingExits = null;
                 Flow.this.make = null;
                 this.thrown = this.caught = null;
                 this.classDef = null;
             }
         }
     }
     /**
      * Specialized pass that performs inference of thrown types for lambdas.
      */
     class LambdaFlowAnalyzer extends FlowAnalyzer {
         List<Type> inferredThrownTypes;
         boolean inLambda;
         @Override
         public void visitLambda(JCLambda tree) {
             if ((tree.type != null &&
                     tree.type.isErroneous()) || inLambda) {
                 return;
             }
             List<Type> prevCaught = caught;
             List<Type> prevThrown = thrown;
             ListBuffer<FlowPendingExit> prevPending = pendingExits;
             inLambda = true;
             try {
                 pendingExits = new ListBuffer<>();
                 caught = List.of(syms.throwableType);
                 thrown = List.nil();
                 scan(tree.body);
                 inferredThrownTypes = thrown;
             } finally {
                 pendingExits = prevPending;
                 caught = prevCaught;
                 thrown = prevThrown;
                 inLambda = false;
             }
         }
         @Override
         public void visitClassDef(JCClassDecl tree) {
             //skip
         }
     }
     /**
      * This pass implements (i) definite assignment analysis, which ensures that
      * each variable is assigned when used and (ii) definite unassignment analysis,
      * which ensures that no final variable is assigned more than once. This visitor
      * depends on the results of the liveliness analyzer. This pass is also used to mark
      * effectively-final local variables/parameters.
      */
     public abstract static class AbstractAssignAnalyzer<P extends AbstractAssignAnalyzer.AbstractAssignPendingExit>
         extends BaseAnalyzer<P> {
         /** The set of definitely assigned variables.
          */
         protected final Bits inits;
         /** The set of definitely unassigned variables.
          */
         final Bits uninits;
         /** The set of variables that are definitely unassigned everywhere
          *  in current try block. This variable is maintained lazily; it is
          *  updated only when something gets removed from uninits,
          *  typically by being assigned in reachable code.  To obtain the
          *  correct set of variables which are definitely unassigned
          *  anywhere in current try block, intersect uninitsTry and
          *  uninits.
          */
         final Bits uninitsTry;
         /** When analyzing a condition, inits and uninits are null.
          *  Instead we have:
          */
         final Bits initsWhenTrue;
         final Bits initsWhenFalse;
         final Bits uninitsWhenTrue;
         final Bits uninitsWhenFalse;
         /** A mapping from addresses to variable symbols.
          */
         protected JCVariableDecl[] vardecls;
         /** The current class being defined.
          */
         JCClassDecl classDef;
         /** The first variable sequence number in this class definition.
          */
         int firstadr;
         /** The next available variable sequence number.
          */
         protected int nextadr;
         /** The first variable sequence number in a block that can return.
          */
         protected int returnadr;
         /** The list of unreferenced automatic resources.
          */
         Scope unrefdResources;
         /** Set when processing a loop body the second time for DU analysis. */
         FlowKind flowKind = FlowKind.NORMAL;
         /** The starting position of the analysed tree */
         int startPos;
         final Symtab syms;
         protected Names names;
         final boolean enforceThisDotInit;
         public static class AbstractAssignPendingExit extends BaseAnalyzer.PendingExit {
             final Bits inits;
             final Bits uninits;
             final Bits exit_inits = new Bits(true);
             final Bits exit_uninits = new Bits(true);
             public AbstractAssignPendingExit(JCTree tree, final Bits inits, final Bits uninits) {
                 super(tree);
                 this.inits = inits;
                 this.uninits = uninits;
                 this.exit_inits.assign(inits);
                 this.exit_uninits.assign(uninits);
             }
             @Override
             public void resolveJump(JCTree tree) {
                 inits.andSet(exit_inits);
                 uninits.andSet(exit_uninits);
             }
         }
         public AbstractAssignAnalyzer(Bits inits, Symtab syms, Names names, boolean enforceThisDotInit) {
             this.inits = inits;
             uninits = new Bits();
             uninitsTry = new Bits();
             initsWhenTrue = new Bits(true);
             initsWhenFalse = new Bits(true);
             uninitsWhenTrue = new Bits(true);
             uninitsWhenFalse = new Bits(true);
             this.syms = syms;
             this.names = names;
             this.enforceThisDotInit = enforceThisDotInit;
         }
         private boolean isInitialConstructor = false;
         @Override
         protected void markDead(JCTree tree) {
             if (!isInitialConstructor) {
                 inits.inclRange(returnadr, nextadr);
             } else {
                 for (int address = returnadr; address < nextadr; address++) {
                     if (!(isFinalUninitializedStaticField(vardecls[address].sym))) {
                         inits.incl(address);
                     }
                 }
             }
             uninits.inclRange(returnadr, nextadr);
         }
         /*-------------- Processing variables ----------------------*/
         /** Do we need to track init/uninit state of this symbol?
          *  I.e. is symbol either a local or a blank final variable?
          */
         protected boolean trackable(VarSymbol sym) {
             return
                 sym.pos >= startPos &&
                 ((sym.owner.kind == MTH ||
                 isFinalUninitializedField(sym)));
         }
         boolean isFinalUninitializedField(VarSymbol sym) {
             return sym.owner.kind == TYP &&
                    ((sym.flags() & (FINAL | HASINIT | PARAMETER)) == FINAL &&
                    classDef.sym.isEnclosedBy((ClassSymbol)sym.owner));
         }
         boolean isFinalUninitializedStaticField(VarSymbol sym) {
             return isFinalUninitializedField(sym) && sym.isStatic();
         }
         /** Initialize new trackable variable by setting its address field
          *  to the next available sequence number and entering it under that
          *  index into the vars array.
          */
         void newVar(JCVariableDecl varDecl) {
             VarSymbol sym = varDecl.sym;
             vardecls = ArrayUtils.ensureCapacity(vardecls, nextadr);
             if ((sym.flags() & FINAL) == 0) {
                 sym.flags_field |= EFFECTIVELY_FINAL;
             }
             sym.adr = nextadr;
             vardecls[nextadr] = varDecl;
             exclVarFromInits(varDecl, nextadr);
             uninits.incl(nextadr);
             nextadr++;
         }
         protected void exclVarFromInits(JCTree tree, int adr) {
             inits.excl(adr);
         }
         protected void assignToInits(JCTree tree, Bits bits) {
             inits.assign(bits);
         }
         protected void andSetInits(JCTree tree, Bits bits) {
             inits.andSet(bits);
         }
         protected void orSetInits(JCTree tree, Bits bits) {
             inits.orSet(bits);
         }
         /** Record an initialization of a trackable variable.
          */
         void letInit(DiagnosticPosition pos, VarSymbol sym) {
             if (sym.adr >= firstadr && trackable(sym)) {
                 if (uninits.isMember(sym.adr)) {
                     uninit(sym);
                 }
                 inits.incl(sym.adr);
             }
         }
         //where
             void uninit(VarSymbol sym) {
                 if (!inits.isMember(sym.adr)) {
                     // reachable assignment
                     uninits.excl(sym.adr);
                     uninitsTry.excl(sym.adr);
                 } else {
                     //log.rawWarning(pos, "unreachable assignment");//DEBUG
                     uninits.excl(sym.adr);
                 }
             }
         /** If tree is either a simple name or of the form this.name or
          *  C.this.name, and tree represents a trackable variable,
          *  record an initialization of the variable.
          */
         void letInit(JCTree tree) {
             tree = TreeInfo.skipParens(tree);
             if (tree.hasTag(IDENT) || tree.hasTag(SELECT)) {
                 Symbol sym = TreeInfo.symbol(tree);
                 if (sym.kind == VAR) {
                     letInit(tree.pos(), (VarSymbol)sym);
                 }
             }
         }
         /** Check that trackable variable is initialized.
          */
         void checkInit(DiagnosticPosition pos, VarSymbol sym) {
             checkInit(pos, sym, "var.might.not.have.been.initialized");
         }
         void checkInit(DiagnosticPosition pos, VarSymbol sym, String errkey) {}
         /** Utility method to reset several Bits instances.
          */
         private void resetBits(Bits... bits) {
             for (Bits b : bits) {
                 b.reset();
             }
         }
         /** Split (duplicate) inits/uninits into WhenTrue/WhenFalse sets
          */
         void split(boolean setToNull) {
             initsWhenFalse.assign(inits);
             uninitsWhenFalse.assign(uninits);
             initsWhenTrue.assign(inits);
             uninitsWhenTrue.assign(uninits);
             if (setToNull) {
                 resetBits(inits, uninits);
             }
         }
         /** Merge (intersect) inits/uninits from WhenTrue/WhenFalse sets.
          */
         protected void merge(JCTree tree) {
             inits.assign(initsWhenFalse.andSet(initsWhenTrue));
             uninits.assign(uninitsWhenFalse.andSet(uninitsWhenTrue));
         }
     /* ************************************************************************
      * Visitor methods for statements and definitions
      *************************************************************************/
         /** Analyze an expression. Make sure to set (un)inits rather than
          *  (un)initsWhenTrue(WhenFalse) on exit.
          */
         void scanExpr(JCTree tree) {
             if (tree != null) {
                 scan(tree);
                 if (inits.isReset()) {
                     merge(tree);
                 }
             }
         }
         /** Analyze a list of expressions.
          */
         void scanExprs(List<? extends JCExpression> trees) {
             if (trees != null)
                 for (List<? extends JCExpression> l = trees; l.nonEmpty(); l = l.tail)
                     scanExpr(l.head);
         }
         /** Analyze a condition. Make sure to set (un)initsWhenTrue(WhenFalse)
          *  rather than (un)inits on exit.
          */
         void scanCond(JCTree tree) {
             if (tree.type.isFalse()) {
                 if (inits.isReset()) merge(tree);
                 initsWhenTrue.assign(inits);
                 initsWhenTrue.inclRange(firstadr, nextadr);
                 uninitsWhenTrue.assign(uninits);
                 uninitsWhenTrue.inclRange(firstadr, nextadr);
                 initsWhenFalse.assign(inits);
                 uninitsWhenFalse.assign(uninits);
             } else if (tree.type.isTrue()) {
                 if (inits.isReset()) merge(tree);
                 initsWhenFalse.assign(inits);
                 initsWhenFalse.inclRange(firstadr, nextadr);
                 uninitsWhenFalse.assign(uninits);
                 uninitsWhenFalse.inclRange(firstadr, nextadr);
                 initsWhenTrue.assign(inits);
                 uninitsWhenTrue.assign(uninits);
             } else {
                 scan(tree);
                 if (!inits.isReset())
                     split(tree.type != syms.unknownType);
             }
             if (tree.type != syms.unknownType) {
                 resetBits(inits, uninits);
             }
         }
         /* ------------ Visitor methods for various sorts of trees -------------*/
         @Override
         public void visitClassDef(JCClassDecl tree) {
             if (tree.sym == null) {
                 return;
             }
             JCClassDecl classDefPrev = classDef;
             int firstadrPrev = firstadr;
             int nextadrPrev = nextadr;
             ListBuffer<P> pendingExitsPrev = pendingExits;
             pendingExits = new ListBuffer<P>();
             if (tree.name != names.empty) {
                 firstadr = nextadr;
             }
             classDef = tree;
             try {
                 // define all the static fields
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(VARDEF)) {
                         JCVariableDecl def = (JCVariableDecl)l.head;
                         if ((def.mods.flags & STATIC) != 0) {
                             VarSymbol sym = def.sym;
                             if (trackable(sym)) {
                                 newVar(def);
                             }
                         }
                     }
                 }
                 // process all the static initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) != 0) {
                         scan(l.head);
                     }
                 }
                 // define all the instance fields
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(VARDEF)) {
                         JCVariableDecl def = (JCVariableDecl)l.head;
                         if ((def.mods.flags & STATIC) == 0) {
                             VarSymbol sym = def.sym;
                             if (trackable(sym)) {
                                 newVar(def);
                             }
                         }
                     }
                 }
                 // process all the instance initializers
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (!l.head.hasTag(METHODDEF) &&
                         (TreeInfo.flags(l.head) & STATIC) == 0) {
                         scan(l.head);
                     }
                 }
                 // process all the methods
                 for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(METHODDEF)) {
                         scan(l.head);
                     }
                 }
             } finally {
                 pendingExits = pendingExitsPrev;
                 nextadr = nextadrPrev;
                 firstadr = firstadrPrev;
                 classDef = classDefPrev;
             }
         }
         @Override
         public void visitMethodDef(JCMethodDecl tree) {
             if (tree.body == null) {
                 return;
             }
             /*  Ignore synthetic methods, except for translated lambda methods.
              */
             if ((tree.sym.flags() & (SYNTHETIC | LAMBDA_METHOD)) == SYNTHETIC) {
                 return;
             }
             final Bits initsPrev = new Bits(inits);
             final Bits uninitsPrev = new Bits(uninits);
             int nextadrPrev = nextadr;
             int firstadrPrev = firstadr;
             int returnadrPrev = returnadr;
             Assert.check(pendingExits.isEmpty());
             boolean lastInitialConstructor = isInitialConstructor;
             try {
                 isInitialConstructor = TreeInfo.isInitialConstructor(tree);
                 if (!isInitialConstructor) {
                     firstadr = nextadr;
                 }
                 for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
                     JCVariableDecl def = l.head;
                     scan(def);
                     Assert.check((def.sym.flags() & PARAMETER) != 0, "Method parameter without PARAMETER flag");
                     /*  If we are executing the code from Gen, then there can be
                      *  synthetic or mandated variables, ignore them.
                      */
                     initParam(def);
                 }
                 // else we are in an instance initializer block;
                 // leave caught unchanged.
                 scan(tree.body);
                 if (isInitialConstructor) {
                     boolean isSynthesized = (tree.sym.flags() &
                                              GENERATEDCONSTR) != 0;
                     for (int i = firstadr; i < nextadr; i++) {
                         JCVariableDecl vardecl = vardecls[i];
                         VarSymbol var = vardecl.sym;
                         if (var.owner == classDef.sym) {
                             // choose the diagnostic position based on whether
                             // the ctor is default(synthesized) or not
                             if (isSynthesized) {
                                 checkInit(TreeInfo.diagnosticPositionFor(var, vardecl),
                                     var, "var.not.initialized.in.default.constructor");
                             } else {
                                 checkInit(TreeInfo.diagEndPos(tree.body), var);
                             }
                         }
                     }
                 }
                 List<P> exits = pendingExits.toList();
                 pendingExits = new ListBuffer<>();
                 while (exits.nonEmpty()) {
                     P exit = exits.head;
                     exits = exits.tail;
                     Assert.check(exit.tree.hasTag(RETURN), exit.tree);
                     if (isInitialConstructor) {
                         assignToInits(exit.tree, exit.exit_inits);
                         for (int i = firstadr; i < nextadr; i++) {
                             checkInit(exit.tree.pos(), vardecls[i].sym);
                         }
                     }
                 }
             } finally {
                 assignToInits(tree, initsPrev);
                 uninits.assign(uninitsPrev);
                 nextadr = nextadrPrev;
                 firstadr = firstadrPrev;
                 returnadr = returnadrPrev;
                 isInitialConstructor = lastInitialConstructor;
             }
         }
         protected void initParam(JCVariableDecl def) {
             inits.incl(def.sym.adr);
             uninits.excl(def.sym.adr);
             }
         public void visitVarDef(JCVariableDecl tree) {
             boolean track = trackable(tree.sym);
             if (track && tree.sym.owner.kind == MTH) {
                 newVar(tree);
             }
             if (tree.init != null) {
                 scanExpr(tree.init);
                 if (track) {
                     letInit(tree.pos(), tree.sym);
                 }
             }
         }
         public void visitBlock(JCBlock tree) {
             int nextadrPrev = nextadr;
             scan(tree.stats);
             nextadr = nextadrPrev;
         }
         int getLogNumberOfErrors() {
             return 0;
         }
         public void visitDoLoop(JCDoWhileLoop tree) {
             ListBuffer<P> prevPendingExits = pendingExits;
             FlowKind prevFlowKind = flowKind;
             flowKind = FlowKind.NORMAL;
             final Bits initsSkip = new Bits(true);
             final Bits uninitsSkip = new Bits(true);
             pendingExits = new ListBuffer<P>();
             int prevErrors = getLogNumberOfErrors();
             do {
                 final Bits uninitsEntry = new Bits(uninits);
                 uninitsEntry.excludeFrom(nextadr);
                 scan(tree.body);
                 resolveContinues(tree);
                 scanCond(tree.cond);
                 if (!flowKind.isFinal()) {
                     initsSkip.assign(initsWhenFalse);
                     uninitsSkip.assign(uninitsWhenFalse);
                 }
                 if (getLogNumberOfErrors() !=  prevErrors ||
                     flowKind.isFinal() ||
                     new Bits(uninitsEntry).diffSet(uninitsWhenTrue).nextBit(firstadr)==-1)
                     break;
                 assignToInits(tree.cond, initsWhenTrue);
                 uninits.assign(uninitsEntry.andSet(uninitsWhenTrue));
                 flowKind = FlowKind.SPECULATIVE_LOOP;
             } while (true);
             flowKind = prevFlowKind;
             assignToInits(tree, initsSkip);
             uninits.assign(uninitsSkip);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitWhileLoop(JCWhileLoop tree) {
             ListBuffer<P> prevPendingExits = pendingExits;
             FlowKind prevFlowKind = flowKind;
             flowKind = FlowKind.NORMAL;
             final Bits initsSkip = new Bits(true);
             final Bits uninitsSkip = new Bits(true);
             pendingExits = new ListBuffer<>();
             int prevErrors = getLogNumberOfErrors();
             final Bits uninitsEntry = new Bits(uninits);
             uninitsEntry.excludeFrom(nextadr);
             do {
                 scanCond(tree.cond);
                 if (!flowKind.isFinal()) {
                     initsSkip.assign(initsWhenFalse) ;
                     uninitsSkip.assign(uninitsWhenFalse);
                 }
                 assignToInits(tree, initsWhenTrue);
                 uninits.assign(uninitsWhenTrue);
                 scan(tree.body);
                 resolveContinues(tree);
                 if (getLogNumberOfErrors() != prevErrors ||
                     flowKind.isFinal() ||
                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1) {
                     break;
                 }
                 uninits.assign(uninitsEntry.andSet(uninits));
                 flowKind = FlowKind.SPECULATIVE_LOOP;
             } while (true);
             flowKind = prevFlowKind;
             //a variable is DA/DU after the while statement, if it's DA/DU assuming the
             //branch is not taken AND if it's DA/DU before any break statement
             assignToInits(tree.body, initsSkip);
             uninits.assign(uninitsSkip);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitForLoop(JCForLoop tree) {
             ListBuffer<P> prevPendingExits = pendingExits;
             FlowKind prevFlowKind = flowKind;
             flowKind = FlowKind.NORMAL;
             int nextadrPrev = nextadr;
             scan(tree.init);
             final Bits initsSkip = new Bits(true);
             final Bits uninitsSkip = new Bits(true);
             pendingExits = new ListBuffer<P>();
             int prevErrors = getLogNumberOfErrors();
             do {
                 final Bits uninitsEntry = new Bits(uninits);
                 uninitsEntry.excludeFrom(nextadr);
                 if (tree.cond != null) {
                     scanCond(tree.cond);
                     if (!flowKind.isFinal()) {
                         initsSkip.assign(initsWhenFalse);
                         uninitsSkip.assign(uninitsWhenFalse);
                     }
                     assignToInits(tree.body, initsWhenTrue);
                     uninits.assign(uninitsWhenTrue);
                 } else if (!flowKind.isFinal()) {
                     initsSkip.assign(inits);
                     initsSkip.inclRange(firstadr, nextadr);
                     uninitsSkip.assign(uninits);
                     uninitsSkip.inclRange(firstadr, nextadr);
                 }
                 scan(tree.body);
                 resolveContinues(tree);
                 scan(tree.step);
                 if (getLogNumberOfErrors() != prevErrors ||
                     flowKind.isFinal() ||
                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1)
                     break;
                 uninits.assign(uninitsEntry.andSet(uninits));
                 flowKind = FlowKind.SPECULATIVE_LOOP;
             } while (true);
             flowKind = prevFlowKind;
             //a variable is DA/DU after a for loop, if it's DA/DU assuming the
             //branch is not taken AND if it's DA/DU before any break statement
             assignToInits(tree.body, initsSkip);
             uninits.assign(uninitsSkip);
             resolveBreaks(tree, prevPendingExits);
             nextadr = nextadrPrev;
         }
         public void visitForeachLoop(JCEnhancedForLoop tree) {
             visitVarDef(tree.var);
             ListBuffer<P> prevPendingExits = pendingExits;
             FlowKind prevFlowKind = flowKind;
             flowKind = FlowKind.NORMAL;
             int nextadrPrev = nextadr;
             scan(tree.expr);
             final Bits initsStart = new Bits(inits);
             final Bits uninitsStart = new Bits(uninits);
             letInit(tree.pos(), tree.var.sym);
             pendingExits = new ListBuffer<P>();
             int prevErrors = getLogNumberOfErrors();
             do {
                 final Bits uninitsEntry = new Bits(uninits);
                 uninitsEntry.excludeFrom(nextadr);
                 scan(tree.body);
                 resolveContinues(tree);
                 if (getLogNumberOfErrors() != prevErrors ||
                     flowKind.isFinal() ||
                     new Bits(uninitsEntry).diffSet(uninits).nextBit(firstadr) == -1)
                     break;
                 uninits.assign(uninitsEntry.andSet(uninits));
                 flowKind = FlowKind.SPECULATIVE_LOOP;
             } while (true);
             flowKind = prevFlowKind;
             assignToInits(tree.body, initsStart);
             uninits.assign(uninitsStart.andSet(uninits));
             resolveBreaks(tree, prevPendingExits);
             nextadr = nextadrPrev;
         }
         public void visitLabelled(JCLabeledStatement tree) {
             ListBuffer<P> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<P>();
             scan(tree.body);
             resolveBreaks(tree, prevPendingExits);
         }
         public void visitSwitch(JCSwitch tree) {
             ListBuffer<P> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<>();
             int nextadrPrev = nextadr;
             scanExpr(tree.selector);
             final Bits initsSwitch = new Bits(inits);
             final Bits uninitsSwitch = new Bits(uninits);
             boolean hasDefault = false;
             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
                 assignToInits(l.head, initsSwitch);
                 uninits.assign(uninits.andSet(uninitsSwitch));
                 JCCase c = l.head;
                 if (c.pat == null) {
                     hasDefault = true;
                 } else {
                     scanExpr(c.pat);
                 }
                 if (hasDefault) {
                     assignToInits(null, initsSwitch);
                     uninits.assign(uninits.andSet(uninitsSwitch));
                 }
                 scan(c.stats);
                 addVars(c.stats, initsSwitch, uninitsSwitch);
                 if (!hasDefault) {
                     assignToInits(l.head.stats.last(), initsSwitch);
                     uninits.assign(uninits.andSet(uninitsSwitch));
                 }
                 // Warn about fall-through if lint switch fallthrough enabled.
             }
             if (!hasDefault) {
                 andSetInits(null, initsSwitch);
             }
             resolveBreaks(tree, prevPendingExits);
             nextadr = nextadrPrev;
         }
         // where
             /** Add any variables defined in stats to inits and uninits. */
             private void addVars(List<JCStatement> stats, final Bits inits,
                                         final Bits uninits) {
                 for (;stats.nonEmpty(); stats = stats.tail) {
                     JCTree stat = stats.head;
                     if (stat.hasTag(VARDEF)) {
                         int adr = ((JCVariableDecl) stat).sym.adr;
                         inits.excl(adr);
                         uninits.incl(adr);
                     }
                 }
             }
         boolean isEnabled(Lint.LintCategory lc) {
             return false;
         }
         void reportWarning(Lint.LintCategory lc, DiagnosticPosition pos, String key, Object ... args) {}
         public void visitTry(JCTry tree) {
             ListBuffer<JCVariableDecl> resourceVarDecls = new ListBuffer<>();
             final Bits uninitsTryPrev = new Bits(uninitsTry);
             ListBuffer<P> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<>();
             final Bits initsTry = new Bits(inits);
             uninitsTry.assign(uninits);
             for (JCTree resource : tree.resources) {
                 if (resource instanceof JCVariableDecl) {
                     JCVariableDecl vdecl = (JCVariableDecl) resource;
                     visitVarDef(vdecl);
                     unrefdResources.enter(vdecl.sym);
                     resourceVarDecls.append(vdecl);
                 } else if (resource instanceof JCExpression) {
                     scanExpr((JCExpression) resource);
                 } else {
                     throw new AssertionError(tree);  // parser error
                 }
             }
             scan(tree.body);
             uninitsTry.andSet(uninits);
             final Bits initsEnd = new Bits(inits);
             final Bits uninitsEnd = new Bits(uninits);
             int nextadrCatch = nextadr;
             if (!resourceVarDecls.isEmpty() &&
                     isEnabled(Lint.LintCategory.TRY)) {
                 for (JCVariableDecl resVar : resourceVarDecls) {
                     if (unrefdResources.includes(resVar.sym)) {
                         reportWarning(Lint.LintCategory.TRY, resVar.pos(),
                                     "try.resource.not.referenced", resVar.sym);
                         unrefdResources.remove(resVar.sym);
                     }
                 }
             }
             /*  The analysis of each catch should be independent.
              *  Each one should have the same initial values of inits and
              *  uninits.
              */
             final Bits initsCatchPrev = new Bits(initsTry);
             final Bits uninitsCatchPrev = new Bits(uninitsTry);
             for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
                 JCVariableDecl param = l.head.param;
                 assignToInits(tree.body, initsCatchPrev);
                 uninits.assign(uninitsCatchPrev);
                 scan(param);
                 /* If this is a TWR and we are executing the code from Gen,
                  * then there can be synthetic variables, ignore them.
                  */
                 initParam(param);
                 scan(l.head.body);
                 initsEnd.andSet(inits);
                 uninitsEnd.andSet(uninits);
                 nextadr = nextadrCatch;
             }
             if (tree.finalizer != null) {
                 assignToInits(tree.finalizer, initsTry);
                 uninits.assign(uninitsTry);
                 ListBuffer<P> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 scan(tree.finalizer);
                 if (!tree.finallyCanCompleteNormally) {
                     // discard exits and exceptions from try and finally
                 } else {
                     uninits.andSet(uninitsEnd);
                     // FIX: this doesn't preserve source order of exits in catch
                     // versus finally!
                     while (exits.nonEmpty()) {
                         P exit = exits.next();
                         if (exit.exit_inits != null) {
                             exit.exit_inits.orSet(inits);
                             exit.exit_uninits.andSet(uninits);
                         }
                         pendingExits.append(exit);
                     }
                     orSetInits(tree, initsEnd);
                 }
             } else {
                 assignToInits(tree, initsEnd);
                 uninits.assign(uninitsEnd);
                 ListBuffer<P> exits = pendingExits;
                 pendingExits = prevPendingExits;
                 while (exits.nonEmpty()) pendingExits.append(exits.next());
             }
             uninitsTry.andSet(uninitsTryPrev).andSet(uninits);
         }
         public void visitConditional(JCConditional tree) {
             scanCond(tree.cond);
             final Bits initsBeforeElse = new Bits(initsWhenFalse);
             final Bits uninitsBeforeElse = new Bits(uninitsWhenFalse);
             assignToInits(tree.cond, initsWhenTrue);
             uninits.assign(uninitsWhenTrue);
             if (tree.truepart.type.hasTag(BOOLEAN) &&
                 tree.falsepart.type.hasTag(BOOLEAN)) {
                 // if b and c are boolean valued, then
                 // v is (un)assigned after a?b:c when true iff
                 //    v is (un)assigned after b when true and
                 //    v is (un)assigned after c when true
                 scanCond(tree.truepart);
                 final Bits initsAfterThenWhenTrue = new Bits(initsWhenTrue);
                 final Bits initsAfterThenWhenFalse = new Bits(initsWhenFalse);
                 final Bits uninitsAfterThenWhenTrue = new Bits(uninitsWhenTrue);
                 final Bits uninitsAfterThenWhenFalse = new Bits(uninitsWhenFalse);
                 assignToInits(tree.truepart, initsBeforeElse);
                 uninits.assign(uninitsBeforeElse);
                 scanCond(tree.falsepart);
                 initsWhenTrue.andSet(initsAfterThenWhenTrue);
                 initsWhenFalse.andSet(initsAfterThenWhenFalse);
                 uninitsWhenTrue.andSet(uninitsAfterThenWhenTrue);
                 uninitsWhenFalse.andSet(uninitsAfterThenWhenFalse);
             } else {
                 scanExpr(tree.truepart);
                 final Bits initsAfterThen = new Bits(inits);
                 final Bits uninitsAfterThen = new Bits(uninits);
                 assignToInits(tree.truepart, initsBeforeElse);
                 uninits.assign(uninitsBeforeElse);
                 scanExpr(tree.falsepart);
                 andSetInits(tree.falsepart, initsAfterThen);
                 uninits.andSet(uninitsAfterThen);
             }
         }
         public void visitIf(JCIf tree) {
             scanCond(tree.cond);
             final Bits initsBeforeElse = new Bits(initsWhenFalse);
             final Bits uninitsBeforeElse = new Bits(uninitsWhenFalse);
             assignToInits(tree.cond, initsWhenTrue);
             uninits.assign(uninitsWhenTrue);
             scan(tree.thenpart);
             if (tree.elsepart != null) {
                 final Bits initsAfterThen = new Bits(inits);
                 final Bits uninitsAfterThen = new Bits(uninits);
                 assignToInits(tree.thenpart, initsBeforeElse);
                 uninits.assign(uninitsBeforeElse);
                 scan(tree.elsepart);
                 andSetInits(tree.elsepart, initsAfterThen);
                 uninits.andSet(uninitsAfterThen);
             } else {
                 andSetInits(tree.thenpart, initsBeforeElse);
                 uninits.andSet(uninitsBeforeElse);
             }
         }
         protected P createNewPendingExit(JCTree tree, Bits inits, Bits uninits) {
             return null;
         }
         @Override
         public void visitBreak(JCBreak tree) {
             recordExit(tree, createNewPendingExit(tree, inits, uninits));
         }
         @Override
         public void visitContinue(JCContinue tree) {
             recordExit(tree, createNewPendingExit(tree, inits, uninits));
         }
         @Override
         public void visitReturn(JCReturn tree) {
             scanExpr(tree.expr);
             recordExit(tree, createNewPendingExit(tree, inits, uninits));
         }
         public void visitThrow(JCThrow tree) {
             scanExpr(tree.expr);
             markDead(tree.expr);
         }
         public void visitApply(JCMethodInvocation tree) {
             scanExpr(tree.meth);
             scanExprs(tree.args);
         }
         public void visitNewClass(JCNewClass tree) {
             scanExpr(tree.encl);
             scanExprs(tree.args);
             scan(tree.def);
         }
         @Override
         public void visitLambda(JCLambda tree) {
             final Bits prevUninits = new Bits(uninits);
             final Bits prevInits = new Bits(inits);
             int returnadrPrev = returnadr;
             ListBuffer<P> prevPending = pendingExits;
             try {
                 returnadr = nextadr;
                 pendingExits = new ListBuffer<P>();
                 for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
                     JCVariableDecl def = l.head;
                     scan(def);
                     inits.incl(def.sym.adr);
                     uninits.excl(def.sym.adr);
                 }
                 if (tree.getBodyKind() == JCLambda.BodyKind.EXPRESSION) {
                     scanExpr(tree.body);
                 } else {
                     scan(tree.body);
                 }
             }
             finally {
                 returnadr = returnadrPrev;
                 uninits.assign(prevUninits);
                 assignToInits(tree, prevInits);
                 pendingExits = prevPending;
             }
         }
         public void visitNewArray(JCNewArray tree) {
             scanExprs(tree.dims);
             scanExprs(tree.elems);
         }
         public void visitAssert(JCAssert tree) {
             final Bits initsExit = new Bits(inits);
             final Bits uninitsExit = new Bits(uninits);
             scanCond(tree.cond);
             uninitsExit.andSet(uninitsWhenTrue);
             if (tree.detail != null) {
                 assignToInits(tree, initsWhenFalse);
                 uninits.assign(uninitsWhenFalse);
                 scanExpr(tree.detail);
             }
             assignToInits(tree, initsExit);
             uninits.assign(uninitsExit);
         }
         public void visitAssign(JCAssign tree) {
             JCTree lhs = TreeInfo.skipParens(tree.lhs);
             if (!isIdentOrThisDotIdent(lhs))
                 scanExpr(lhs);
             scanExpr(tree.rhs);
             letInit(lhs);
         }
         private boolean isIdentOrThisDotIdent(JCTree lhs) {
             if (lhs.hasTag(IDENT))
                 return true;
             if (!lhs.hasTag(SELECT))
                 return false;
             JCFieldAccess fa = (JCFieldAccess)lhs;
             return fa.selected.hasTag(IDENT) &&
                    ((JCIdent)fa.selected).name == names._this;
         }
         // check fields accessed through this.<field> are definitely
         // assigned before reading their value
         public void visitSelect(JCFieldAccess tree) {
             super.visitSelect(tree);
             if (enforceThisDotInit &&
                 tree.selected.hasTag(IDENT) &&
                 ((JCIdent)tree.selected).name == names._this &&
                 tree.sym.kind == VAR)
             {
                 checkInit(tree.pos(), (VarSymbol)tree.sym);
             }
         }
         public void visitAssignop(JCAssignOp tree) {
             scanExpr(tree.lhs);
             scanExpr(tree.rhs);
             letInit(tree.lhs);
         }
         public void visitUnary(JCUnary tree) {
             switch (tree.getTag()) {
             case NOT:
                 scanCond(tree.arg);
                 final Bits t = new Bits(initsWhenFalse);
                 initsWhenFalse.assign(initsWhenTrue);
                 initsWhenTrue.assign(t);
                 t.assign(uninitsWhenFalse);
                 uninitsWhenFalse.assign(uninitsWhenTrue);
                 uninitsWhenTrue.assign(t);
                 break;
             case PREINC: case POSTINC:
             case PREDEC: case POSTDEC:
                 scanExpr(tree.arg);
                 letInit(tree.arg);
                 break;
             default:
                 scanExpr(tree.arg);
             }
         }
         public void visitBinary(JCBinary tree) {
             switch (tree.getTag()) {
             case AND:
                 scanCond(tree.lhs);
                 final Bits initsWhenFalseLeft = new Bits(initsWhenFalse);
                 final Bits uninitsWhenFalseLeft = new Bits(uninitsWhenFalse);
                 assignToInits(tree.lhs, initsWhenTrue);
                 uninits.assign(uninitsWhenTrue);
                 scanCond(tree.rhs);
                 initsWhenFalse.andSet(initsWhenFalseLeft);
                 uninitsWhenFalse.andSet(uninitsWhenFalseLeft);
                 break;
             case OR:
                 scanCond(tree.lhs);
                 final Bits initsWhenTrueLeft = new Bits(initsWhenTrue);
                 final Bits uninitsWhenTrueLeft = new Bits(uninitsWhenTrue);
                 assignToInits(tree.lhs, initsWhenFalse);
                 uninits.assign(uninitsWhenFalse);
                 scanCond(tree.rhs);
                 initsWhenTrue.andSet(initsWhenTrueLeft);
                 uninitsWhenTrue.andSet(uninitsWhenTrueLeft);
                 break;
             default:
                 scanExpr(tree.lhs);
                 scanExpr(tree.rhs);
             }
         }
         public void visitIdent(JCIdent tree) {
             if (tree.sym.kind == VAR) {
                 checkInit(tree.pos(), (VarSymbol)tree.sym);
                 referenced(tree.sym);
             }
         }
         void referenced(Symbol sym) {
             unrefdResources.remove(sym);
         }
         public void visitAnnotatedType(JCAnnotatedType tree) {
             // annotations don't get scanned
             tree.underlyingType.accept(this);
         }
         public void visitTopLevel(JCCompilationUnit tree) {
             // Do nothing for TopLevel since each class is visited individually
         }
     /**************************************************************************
      * main method
      *************************************************************************/
         /** Perform definite assignment/unassignment analysis on a tree.
          */
         public void analyzeTree(Env<?> env) {
             analyzeTree(env, env.tree);
          }
         public void analyzeTree(Env<?> env, JCTree tree) {
             try {
                 startPos = tree.pos().getStartPosition();
                 if (vardecls == null)
                     vardecls = new JCVariableDecl[32];
                 else
                     for (int i=0; i<vardecls.length; i++)
                         vardecls[i] = null;
                 firstadr = 0;
                 nextadr = 0;
                 pendingExits = new ListBuffer<>();
                 this.classDef = null;
                 unrefdResources = new Scope(env.enclClass.sym);
                 scan(tree);
             } finally {
                 // note that recursive invocations of this method fail hard
                 startPos = -1;
                 resetBits(inits, uninits, uninitsTry, initsWhenTrue,
                         initsWhenFalse, uninitsWhenTrue, uninitsWhenFalse);
                 if (vardecls != null) {
                     for (int i=0; i<vardecls.length; i++)
                         vardecls[i] = null;
                 }
                 firstadr = 0;
                 nextadr = 0;
                 pendingExits = null;
                 this.classDef = null;
                 unrefdResources = null;
             }
         }
     }
     public static class AssignAnalyzer
         extends AbstractAssignAnalyzer<AssignAnalyzer.AssignPendingExit> {
         Log log;
         Lint lint;
         public static class AssignPendingExit
             extends AbstractAssignAnalyzer.AbstractAssignPendingExit {
             public AssignPendingExit(JCTree tree, final Bits inits, final Bits uninits) {
                 super(tree, inits, uninits);
             }
         }
         public AssignAnalyzer(Log log, Symtab syms, Lint lint, Names names, boolean enforceThisDotInit) {
             super(new Bits(), syms, names, enforceThisDotInit);
             this.log = log;
             this.lint = lint;
         }
         @Override
         protected AssignPendingExit createNewPendingExit(JCTree tree,
             Bits inits, Bits uninits) {
             return new AssignPendingExit(tree, inits, uninits);
         }
         /** Record an initialization of a trackable variable.
          */
         @Override
         void letInit(DiagnosticPosition pos, VarSymbol sym) {
             if (sym.adr >= firstadr && trackable(sym)) {
                 if ((sym.flags() & EFFECTIVELY_FINAL) != 0) {
                     if (!uninits.isMember(sym.adr)) {
                         //assignment targeting an effectively final variable
                         //makes the variable lose its status of effectively final
                         //if the variable is _not_ definitively unassigned
                         sym.flags_field &= ~EFFECTIVELY_FINAL;
                     } else {
                         uninit(sym);
                     }
                 }
                 else if ((sym.flags() & FINAL) != 0) {
                     if ((sym.flags() & PARAMETER) != 0) {
                         if ((sym.flags() & UNION) != 0) { //multi-catch parameter
                             log.error(pos, "multicatch.parameter.may.not.be.assigned", sym);
                         }
                         else {
                             log.error(pos, "final.parameter.may.not.be.assigned",
                                   sym);
                         }
                     } else if (!uninits.isMember(sym.adr)) {
                         log.error(pos, flowKind.errKey, sym);
                     } else {
                         uninit(sym);
                     }
                 }
                 inits.incl(sym.adr);
             } else if ((sym.flags() & FINAL) != 0) {
                 log.error(pos, "var.might.already.be.assigned", sym);
             }
         }
         @Override
         void checkInit(DiagnosticPosition pos, VarSymbol sym, String errkey) {
             if ((sym.adr >= firstadr || sym.owner.kind != TYP) &&
                 trackable(sym) &&
                 !inits.isMember(sym.adr)) {
                 log.error(pos, errkey, sym);
                 inits.incl(sym.adr);
             }
         }
         @Override
         void reportWarning(Lint.LintCategory lc, DiagnosticPosition pos,
             String key, Object ... args) {
             log.warning(lc, pos, key, args);
         }
         @Override
         int getLogNumberOfErrors() {
             return log.nerrors;
         }
         @Override
         boolean isEnabled(Lint.LintCategory lc) {
             return lint.isEnabled(lc);
         }
         @Override
         public void visitClassDef(JCClassDecl tree) {
             if (tree.sym == null) {
                 return;
             }
             Lint lintPrev = lint;
             lint = lint.augment(tree.sym);
             try {
                 super.visitClassDef(tree);
             } finally {
                 lint = lintPrev;
             }
         }
         @Override
         public void visitMethodDef(JCMethodDecl tree) {
             if (tree.body == null) {
                 return;
             }
             /*  MemberEnter can generate synthetic methods ignore them
              */
             if ((tree.sym.flags() & SYNTHETIC) != 0) {
                 return;
             }
             Lint lintPrev = lint;
             lint = lint.augment(tree.sym);
             try {
                 super.visitMethodDef(tree);
             } finally {
                 lint = lintPrev;
             }
         }
         @Override
         public void visitVarDef(JCVariableDecl tree) {
             if (tree.init == null) {
                 super.visitVarDef(tree);
             } else {
                 Lint lintPrev = lint;
                 lint = lint.augment(tree.sym);
                 try{
                     super.visitVarDef(tree);
                 } finally {
                     lint = lintPrev;
                 }
             }
         }
     }
     /**
      * This pass implements the last step of the dataflow analysis, namely
      * the effectively-final analysis check. This checks that every local variable
      * reference from a lambda body/local inner class is either final or effectively final.
      * As effectively final variables are marked as such during DA/DU, this pass must run after
      * AssignAnalyzer.
      */
     class CaptureAnalyzer extends BaseAnalyzer<BaseAnalyzer.PendingExit> {
         JCTree currentTree; //local class or lambda
         @Override
         void markDead(JCTree tree) {
             //do nothing
         }
         @SuppressWarnings("fallthrough")
         void checkEffectivelyFinal(DiagnosticPosition pos, VarSymbol sym) {
             if (currentTree != null &&
                     sym.owner.kind == MTH &&
                     sym.pos < currentTree.getStartPosition()) {
                 switch (currentTree.getTag()) {
                     case CLASSDEF:
                         if (!allowEffectivelyFinalInInnerClasses) {
                             if ((sym.flags() & FINAL) == 0) {
                                 reportInnerClsNeedsFinalError(pos, sym);
                             }
                             break;
                         }
                     case LAMBDA:
                         if ((sym.flags() & (EFFECTIVELY_FINAL | FINAL)) == 0) {
                            reportEffectivelyFinalError(pos, sym);
                         }
                 }
             }
         }
         @SuppressWarnings("fallthrough")
         void letInit(JCTree tree) {
             tree = TreeInfo.skipParens(tree);
             if (tree.hasTag(IDENT) || tree.hasTag(SELECT)) {
                 Symbol sym = TreeInfo.symbol(tree);
                 if (currentTree != null &&
                         sym.kind == VAR &&
                         sym.owner.kind == MTH &&
                         ((VarSymbol)sym).pos < currentTree.getStartPosition()) {
                     switch (currentTree.getTag()) {
                         case CLASSDEF:
                             if (!allowEffectivelyFinalInInnerClasses) {
                                 reportInnerClsNeedsFinalError(tree, sym);
                                 break;
                             }
                         case LAMBDA:
                             reportEffectivelyFinalError(tree, sym);
                     }
                 }
             }
         }
         void reportEffectivelyFinalError(DiagnosticPosition pos, Symbol sym) {
             String subKey = currentTree.hasTag(LAMBDA) ?
                   "lambda"  : "inner.cls";
             log.error(pos, "cant.ref.non.effectively.final.var", sym, diags.fragment(subKey));
         }
         void reportInnerClsNeedsFinalError(DiagnosticPosition pos, Symbol sym) {
             log.error(pos,
                     "local.var.accessed.from.icls.needs.final",
                     sym);
         }
     /*************************************************************************
      * Visitor methods for statements and definitions
      *************************************************************************/
         /* ------------ Visitor methods for various sorts of trees -------------*/
         public void visitClassDef(JCClassDecl tree) {
             JCTree prevTree = currentTree;
             try {
                 currentTree = tree.sym.isLocal() ? tree : null;
                 super.visitClassDef(tree);
             } finally {
                 currentTree = prevTree;
             }
         }
         @Override
         public void visitLambda(JCLambda tree) {
             JCTree prevTree = currentTree;
             try {
                 currentTree = tree;
                 super.visitLambda(tree);
             } finally {
                 currentTree = prevTree;
             }
         }
         @Override
         public void visitIdent(JCIdent tree) {
             if (tree.sym.kind == VAR) {
                 checkEffectivelyFinal(tree, (VarSymbol)tree.sym);
             }
         }
         public void visitAssign(JCAssign tree) {
             JCTree lhs = TreeInfo.skipParens(tree.lhs);
             if (!(lhs instanceof JCIdent)) {
                 scan(lhs);
             }
             scan(tree.rhs);
             letInit(lhs);
         }
         public void visitAssignop(JCAssignOp tree) {
             scan(tree.lhs);
             scan(tree.rhs);
             letInit(tree.lhs);
         }
         public void visitUnary(JCUnary tree) {
             switch (tree.getTag()) {
                 case PREINC: case POSTINC:
                 case PREDEC: case POSTDEC:
                     scan(tree.arg);
                     letInit(tree.arg);
                     break;
                 default:
                     scan(tree.arg);
             }
         }
         public void visitTopLevel(JCCompilationUnit tree) {
             // Do nothing for TopLevel since each class is visited individually
         }
     /**************************************************************************
      * main method
      *************************************************************************/
         /** Perform definite assignment/unassignment analysis on a tree.
          */
         public void analyzeTree(Env<AttrContext> env, TreeMaker make) {
             analyzeTree(env, env.tree, make);
         }
         public void analyzeTree(Env<AttrContext> env, JCTree tree, TreeMaker make) {
             try {
                 attrEnv = env;
                 Flow.this.make = make;
                 pendingExits = new ListBuffer<PendingExit>();
                 scan(tree);
             } finally {
                 pendingExits = null;
                 Flow.this.make = null;
             }
         }
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/comp/Flow.java@12f99d1f23d9 (annotated)

src/share/classes/com/sun/tools/javac/comp/Flow.java